Beosin: JPEG'd attack reason is reentrancy attack

ChainCatcher message, according to the analysis by the Beosin security team, the root cause of the attack on the JPEG'd project lies in a reentrancy issue.

It is reported that the attacker added liquidity through reentrancy into the addliquidity function while calling the removeliquidity function to remove liquidity. Since the balance update occurs before reentrancy into the add_liquidity function, this leads to an error in price calculation.